The present invention relates to a novel polyimide resin and a resin composition, an adhesive solution, a film-state joining component, and an adhesive laminate film which comprise the polyimide resin and to production methods therefor. The present invention is useful as a material for an adhesive having excellent heat resistance and adhesion, which is used for a flexible printed circuit board, a tape for TAB (Tape Automated Bonding), a composite lead frame, and a lamination material, or the like. Further, it relates to a laminate film suitable for a wire rod coating for superconductivity.
Recently, downsizing and weight reduction of electronic parts has been demanded, as electronic devices have been more and more efficient, highly functional, and downsized. Therefore, packaging methods of semiconductor elements as well as higher density, higher efficiency, and higher function of wiring materials or parts for packaging have also been demanded. Especially, there has been a demand for materials showing excellent adhesion which may be preferably used as high-density packaging materials, such as semiconductor packages, COL (Chip on Lead) packages, LOC (Lead on Chip) packages, and MCM (Multi Chip Module) or the like, and printed-wiring board materials such as multiplayer FPC (Flexible Printed Circuit) as well as aerospace materials.
Conventionally, adhesives such as acrylic adhesives, phenol-type adhesives, epoxy-type adhesives, and polyimide-type adhesives or the like are known for their superior mechanical characteristics, heat resistance, and insulating properties in semiconductor packages and other packaging materials.
Phenol-type and epoxy-type adhesives with excellent adhesion are, however, poor in flexibility. There was a problem that acrylic adhesives having excellent flexibility are poor in heat resistance.
In order to solve the aforesaid problems, polyimide is to be used. Among a variety of organic polymers, polyimide is in widespread application of the aerospace field to the electronic communications field and is also used as an adhesive because of its excellent heat resistance. However, a high temperature around 300xc2x0 C. and high pressure are required for bonding of a polyimide adhesive having excellent heat resistance, whose adhesive strength is not such high. Further, since a conventional polyimide adhesive has high water absorption and contains many residual volatile components (the absorbed moisture and the solvent used for producing an adhesive), for example, a problem such as swelling has easily arisen when a lead frame using this polyimide adhesive is dip-soldered.
Furthermore, polyimide is soluble only in a few kinds of solvents, such as N,N-dimethylformaide, DMAc, and NMP (N-methylpyrrolidone) or the like because of its very poor solubility in organic solvents. In addition, it has revealed that these high-boiling solvents are not fully removable even after drying of the adhesive solution applied onto a film, therefore, the residual solvent content in the film leads to a cause of foaming.
On the other hand, recent development of elementary particle physics has accelerated to build particle accelerators which generate further high energy. For the high energy to be generated, an electromagnet, which can generate high magnetic fields by the passage of a large current, is needed. The use of superconductive magnets with superconductive wire rods have been increased. An oxide having copper as the main constituent is often used as a material for a superconductive wire rod. Characteristics of the electromagnet may be deteriorated by variations in the oxidization condition of the superconductive wire rod by heating when a thermosetting adhesive is used to coat a superconductive wire rod with an insulating coating material. It is, therefore, essential for such application to use an adhesive which can be cured and bonded at low temperatures.
Further, accelerators are devices which accelerate elementary particles, such as protons and electrons, and make protons and protons, and electrons and electrons to decay by colliding them each other and examine particles emitted from the decay, wherein a great amount of radiation is generated considering from the nature of the devices. Accordingly, superior radiation resistance is required for insulating coating materials and adhesives.
In the application for these superconductive magnets, particularly in the coating of wire rods for superconductivity used at an extremely low temperature, laminates made by depositing thermosetting resins having epoxy resin as the main agent on polyimide films have been used so far.
In this case, however, epoxy resins do not show sufficient radiation resistance. In addition, in the future, radiation resistance is increasingly required because the amount of radiation is estimated to increase with growth of energy of accelerators. Furthermore, polyimide can be listed as thermal fused layers with excellent radiation resistance, however, it has become a problem that the thermal fused polyimide is bonded at a high temperature, while polyimide which can be bonded at a low temperature is poor in heat resistance, adhesion, and resins squeezing out at pressing. To solve the above problems, adhesives which can be bonded at low temperatures and have excellent radiation resistance have been needed.
Accordingly, it is an object of the present invention to provide a polyimide resin which is excellent in low water absorption, heat resistant for solders, heat resistance, and adhesion.
It is another object of the present invention to provide a resin composition which comprises a polyimide resin capable of being cured to be bonded at a relatively low temperature, and is soluble in solvent and excellent in heat resistance and adhesion.
It is further another object of the present invention to provide an adhesive solution wherein a solvent is easily removable from a film while keeping its heat resistance and adhesion, and a joining component in a film state obtained by using the adhesive solution.
It is still another object of the present invention to develop an adhesive laminate film for wire rod coating which is excellent in flexibility and adhesion, and the like without any deterioration of the wire rod when coating with it.
The polyimide resin of the present invention is obtained by reacting tetracarboxylic acid dianhydride containing ester acid dianhydride represented by the general formula (1): 
wherein X represents xe2x80x94(CH2)kxe2x80x94, or is a divalent group which comprises an aromatic ring; k is an integer from 1 to 10; with diamine containing an aromatic diamine represented by the general formula (2): 
wherein R1 represents alkyl, fluoro-alkyl, and alkoxyl groups or a halogen group; n may be an integer from 0 to 4; and R1 whose number is n is the same or different; and/or an aromatic diamine represented by the general formula (3): 
wherein A is at least one selected from the groups consisting of a single bond, xe2x80x94Oxe2x80x94, xe2x80x94(CH2)nxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94C(xe2x95x90O)Oxe2x80x94, xe2x80x94NHCOxe2x80x94, xe2x80x94C(CH3)2xe2x80x94, xe2x80x94C(CF3)2xe2x80x94, xe2x80x94Sxe2x80x94, or xe2x80x94SO2xe2x80x94, R2, R3, and R4 represent independently alkyl, fluoro-alkyl, and alkoxyl groups or a halogen group, and are the same or different, x, y, z, m, and n are each an integer from 0 to 4. A whose number is n (m+1) may be respectively the same or different.
Or the polyimide resin of the present invention is obtained by a reaction between tetracarboxylic acid dianhydride containing ester acid dianhydride represented by the general formula (1): 
wherein X represents xe2x80x94(CH2)kxe2x80x94 or is a divalent group which comprises an aromatic ring; k is an integer from 1 to 10); and aromatic diamine represented by the general formula (4): 
wherein Y is at least one selected from the groups consisting of a single bond, xe2x80x94COxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94(CH2)qxe2x80x94, xe2x80x94NHCOxe2x80x94, xe2x80x94C(CH3)2xe2x80x94, xe2x80x94C(CF3)2xe2x80x94, or xe2x80x94C(xe2x95x90O)Oxe2x80x94; p and q are each an integer from 1 to 5.
Further, the polyimide resin of the present invention is obtained by reacting tetracarboxylic acid dianhydride containing ester-acid dianhydride represented by the general formula (1): 
wherein X represents xe2x80x94(CH2)kxe2x80x94 or is a divalent group comprising an aromatic ring; k is an integer from 1 to 10; with aromatic diamine represented by the general formula (4): 
wherein Y is at least one selected from the groups consisting of a single bond, xe2x80x94COxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94(CH2)qxe2x80x94, xe2x80x94NHCOxe2x80x94, xe2x80x94C(CH3)2xe2x80x94, xe2x80x94C(CF3)2xe2x80x94, or xe2x80x94C(xe2x95x90O)Oxe2x80x94; p and q are each an integer from 1 to 5; and siloxane diamine represented by the general formula (5): 
Wherein R5 and R6 are each a divalent aliphatic group whose carbon number is from 1 to 4 or a divalent aromatic group, R7, R8, R9, and R10 are each a monovalent aliphatic group whose carbon number is from 1 to 4 or a monovalent aromatic group; n is an integer from 1 to 10.
Other general explanation of the polyimide resin of the present invention is that the polyimide resin is obtained by a reaction among tetracarboxylic acid dianhydride containing 2,2-(4-hydroxyphenyl) propanedibenzoate-3,3xe2x80x24,4xe2x80x2-tetracarboxylic acid dianhydride represented by the general formula (7):, and 
aromatic diarine represented by the general formula (2): 
Wherein R1 represents alkyl, fluoro-alkyl, and alkoxyl groups or a halogen group; n is an integer from 0 to 4; R1 whose number is n may be the same or different, and/or diamine containing aromatic diamine represented by the general formula (3): 
wherein A is at least one selected from the groups consisting of a single bond, xe2x80x94Oxe2x80x94, xe2x80x94(CH2)nxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94C(xe2x95x90O)Oxe2x80x94, xe2x80x94NHCOxe2x80x94, xe2x80x94C(CH3)2xe2x80x94, xe2x80x94C(CF3)2xe2x80x94, xe2x80x94Sxe2x80x94, or xe2x80x94SO2xe2x80x94; R2, R3, and R4 represent independently alkyl, fluoro-alkyl, and alkoxyl groups or a halogen group, and may be the same or different; x, y, z, m, and n are each an integer from 0 to 4; and A whose number is (m+1) may be respectively the same or different.
Tetracarboxylic acid dianhydride containing 2,2-(4-hydroxyphenyl) propanedibenzoate-3,3xe2x80x24,4xe2x80x2-tetracarboxylic acid dianhydride represented by the general formula (7) can be adjusted to have a residual impurities content of 1 wt % or lower. 
These polyimide resins may have both a glass transition temperature from 100xc2x0 C. to 250xc2x0 C. and water absorption of 1.5% or lower.
Further, the resin composition of the present invention comprises the polyimide resin and a thermosetting resin.
The resin composition of the present invention may have water absorption after cured of 1.5% or lower.
Furthermore, the resin composition of the present invention may have a residual volatile component of 3 wt % or lower.
Further, the polyimide resin may be a resin composition which is an amine-terminated polyimide oligomer.
The cured resin of the present invention obtained by curing the above-mentioned resin composition may have water absorption of 1.5% or lower.
Its residual volatile component may be 3 wt % or lower.
The polyimide adhesive solution of the present invention is comprised the above polyimide resin, epoxy resin, and curing agent, wherein 50 mole % or more of a dianhydride residue included in the polyimide resin is an ester-acid dianhydride residue represented by the general formula (1): 
wherein X, represents xe2x80x94(CH2)kxe2x80x94, or is a divalent group which comprises an aromatic ring; and k is an integer from 1 to 10; and the organic solvent may include a cyclic ether solvent.
The general description of the film-state joining component of the present invention is formed by laminating a thermosetting resin on one side or both sides of a base film with a main constituent of the above polyimide resin.
Other general description of the film-state joining component of the present invention is formed by laminating the above resin composition on one side or both sides of the polyimide base film. Further, the film-state joining component of the present invention is obtained by dissolving the above resin composition in an organic solvent and applying or flow casting the composition onto a support, and subsequently depositing the film-like resin composition layer obtained by peeling off a coating film from the support after being dried. Or the film-state joining component is obtained by dissolving the above mentioned resin composition in an organic solvent and applying or flow casting the composition onto at least one side of the polyimide base film, and drying it subsequently. In addition, the film-state joining component of the present invention is obtained by applying the above polyimide adhesive solution by applying or flow casting onto the support and peeling off the adhesive coating film from the support after being dried. Or the film-state joining component is obtained by applying the above polyimide adhesive solution or flow casting it onto at least one side of the polyimide base film and drying it subsequently.
Moreover, the above mentioned film-state joining component may be used for the adhesive laminate film for wire rod coating.